Question

Principal weather parameters affecting evapotranspiration are:
A. Reflection
B. Solar radiation
C. Crop roughness
D. Air temperature
E. Wind speed

• A. A, D, C only
• B. B, C, D only
• C. B, D, E only
• D. A, B, D, E only

Hint:

To remember the drivers of ET, think of what makes clothes dry faster: Sun (Radiation), Heat (Temperature), and Wind (Wind Speed).

Answer 1

The Correct Option is C

Concept: Evapotranspiration (ET) is the combined process of water loss from the soil surface (evaporation) and from the plant tissues (transpiration). While "Crop roughness" (C) is a biological factor, the question specifically asks for weather parameters.

Step 1: Identify the energy driver for ET.
Solar radiation (B) is the primary weather parameter. It provides the latent heat required to transform liquid water into water vapor. Without radiation, the process of ET would be negligible.

Step 2: Identify the atmospheric demand factors.
Air temperature (D) influences the vapor pressure deficit; warmer air can hold more moisture, increasing the rate of ET. Wind speed (E) is crucial as it removes the saturated air layer near the plant or soil surface (boundary layer), replacing it with drier air and thus maintaining a steep concentration gradient for continued ET.

Step 3: Eliminate non-weather or secondary factors.
"Reflection" (A) is a property of the surface (albedo), not a weather parameter itself. "Crop roughness" (C) is a physical characteristic of the vegetation canopy, not a weather parameter. Thus, B, D, and E are the principal weather-related drivers.